In Montgomery County, roof drains shall not be connected to streets,
sanitary or storm sewers, or roadside ditches, and shall discharge
to infiltration areas or vegetative BMPs to the maximum extent practicable,
except for already existing developed sites where the on-site stormwater
system already is designed and equipped to accomplish stormwater rate,
quality, and quantity mitigation. The applicant shall, in these cases,
submit documentation on the existing stormwater system to the Municipal
Engineer, who shall determine if the stormwater system accomplishes
comparable stormwater rate, quality, and quantity mitigation.